1996dodge caravan wont reverse why?

You drained transmission fluid from the tranny? Use the dipstick and put back the proper amount, do you have reason to believe it got overfilled? If it goes into gear and shifts properly driving regularly, there is something wrong besides the fluid level. I don't now if on your particular car you check it while running, some do, others not. Google your car..just put in the search box the keywords, your make/model/year trim and somewhere there will be a site that will tell you

could it be a shift silonoid if the van still moves when ni put it in drive